Non-contrast MR Angiography

Figure 1. NC-MRA (inflow inversion recovery) shows normal arterial vasculature of the lower extremities. PA, popliteal artery; AT, anterior tibial arteries; PT, posterior tibial arteries; and PER, peroneal arteries. Techniques for performing non-contrast MR angiography (NC-MRA) have been available since the introduction of MR imaging. These techniques were largely displaced by contrast-enhanced MR angiography (CE-MRA) owing to shorter acquisition times, greater anatomical coverage, and decreased pulsatility and flow artifacts. However, recent concerns about the safety of gadolinium-based contrast materials in highrisk patients, specifically in patients with renal failure, have revived interest in NC-MRA. At the same time, the initial disadvantages of NC-MRA have largely been overcome by advances in scanner hardware, the development of new imaging sequences, and the advent of cardiac and respiratory gating. NC-MRA also offers intrinsic advantages beyond, or in addition to, CEMRA. For example, NC-MRA does not require precise timing of a power-injected bolus, while CE-MRA relies on perfect timing of the first pass of contrast through the arterial or venous circulation. The timing of this acquisition can be a challenge in the presence of cardiac disease, vascular disease, or difficult intravenous access. NC-MRA also allows for multiple acquisitions, whereas CE-MRA is a "single-shot" technique.